The pre-modern Silk Routes were so named because they primarily carried:

1. NCERT discusses the Silk Routes extensively. 2. Chinese silk cargoes travelling these routes gave them their name. 3. The routes existed on land and by sea, linking vast regions of Asia, North Africa and Europe. _Source: NCERT Class 10 History India and the Contemporary World - II, Ch 3 "The Making of a Global World", §Silk Routes ¶1_